Recently, the concern for monitoring water quality has increased world-wide. An area of particular concern is the release of health hazardous compounds, such as pharmaceuticals, pesticides, toxins etc. into the environment. Such compounds may persist in ground water and any other water that humans are exposed to.
The monitoring of hazardous compounds is crucial to ensure that the water people are exposed to is safe and free from contaminants that could cause health problems.
To date, several detection techniques exist, but monitoring water for chemical contaminants is difficult for a variety of reasons. For example, many compounds are present at very low concentrations making detection difficult. Furthermore, the detection sensitivity is often decreased by inhibitory compounds which may be present in environmental concentrates. As a result, many false positive signals are produced.
Currently, the research in the field of molecularly imprinted polymers, hereinafter referred to as MIPs, is accelerating. MIPs have attracted a lot of attention due to their ability to specifically recognize compounds such as drugs, hormones, proteins etc.
Molecular imprinting is a generic technology, which introduces recognition properties into synthetic polymers. MIPs are fabricated by synthesising highly cross-linked polymers from a mixture of functional monomers in the presence of an analyte, which functions as a template. After extraction of the analyte with a solvent, a molecular imprint is left in the polymer, which can recognise the same template molecule or its analogues.
MIPs are not as specific as antibodies, but possess high affinity towards specific targets (e.g., caffeine or sorbitol, see Feng, L. et. al. Biosensor for the determination of sorbitol based on molecularly imprinted electrosynthesized polymers. Biosensors & Bioelectronics, 2004, 19, 1513-1519) and usually have non-negligible affinity to similar molecules (e.g., MIPs prepared against Penicillin G display high affinity for not only the original template, but also other related β-lactam antibiotics, see Benito-Pena, E. et al. Molecular engineering of fluorescent penicillins for molecularly imprinted polymer assays. Anal. Chem., 2006, 78, 2019-2027).
Depending on the application this may be a disadvantage, but it may be advantageous, too. For example, if one considers to apply the MIP-based sensing system to monitor environmental contaminants, e.g., pharmacological compounds in drinking water, one does not need to manufacture different MIPs for each contaminant, but only to each family of contaminants.
Current detection schemes, such as chromatography or electrophoresis paired with chemical sample treatment, and solid phase based extraction e.g. via MIP are time-consuming and unsuitable for use in or at the field. These techniques require the collection of a waste-water sample to be transported into a lab, where labor extensive extraction and analysis is required to detect the presence of a target compound of interest.
Furthermore, the MIP detection schemes currently available suffer from the generation of many false-positive signals, especially where MIPs have been produced by non-covalent imprinting.
Accordingly, there is a need in the art to provide an alternative approach for the detection of target molecules of interests, e.g. contaminants present in water and other environmental concentrates. Such a method should be convenient, inexpensive and prevent the generation of false-positive signals to a substantial degree. More specifically, such an approach should be capable of detection of target molecules in their actual contexts; i.e. in the environment where they are found; e.g. ground or waste water.